President Erdogan is holding his final rally in Istanbul and says he is confident of victory.

He assumed the presidency, a largely ceremonial position, in 2014 after more than a decade as prime minister.

“No” campaigners fear increasingly authoritarian rule

The referendum on constitutional change would abolish the post of PM, allowing the president to appoint cabinet ministers and bring all state bureaucracy under his control.

The president says the new system will resemble those in France and the US and will bring stability in a time of turmoil marked by a Kurdish insurgency, Islamist militancy and conflict in neighbouring Syria that has led to a huge refugee influx.

What’s in the new constitution?

The president would be able to directly appoint top public officials, including ministers

He would also be able to assign one or several vice-presidents

The job of prime minister, currently held by Binali Yildirim, would be scrapped

The president would have power to intervene in the judiciary, which Mr Erdogan has accused of being influenced by Fethullah Gulen, the Pennsylvania-based preacher he blames for the July 2016 coup against him

The president would decide whether or not impose a state of emergency

Critics fear the change would put too much power in the president’s grasp, amounting to one-man rule, without the checks and balances of other presidential systems.

They say his ability to retain ties to a political party – Mr Erdogan could resume leadership of the AK Party (AKP) he co-founded – would end any chance of presidential impartiality.

The referendum has a simple “yes” or “no” choice on whether to endorse parliament’s approval of a new draft constitution.

The draft states that the next presidential and parliamentary elections will be held on November 3, 2019.

The president would have a five-year tenure, for a maximum of two terms.

Campaigning on the referendum will continue until 18:00 (15:00 GMT) on Saturday, with voting getting under way in the country’s east at 07:00 (0400 GMT) on Sunday and an hour later elsewhere.